Management of anemia in patients with end stage renal disease (ESRD) requires careful monitoring of iron status. Although serum ferritin is used as an indicator of iron stores, its value is limited because ferritin is an acute-phase reactant; its level increases sharply in the presence of inflammation and infection. This article presents information on the value and limitations of serum ferritin as a marker of storage iron in healthy individuals and in patients with ESRD. It also discusses the need to consider the percentage of transferrin saturation, total iron-binding capacity, and immature reticulocyte fraction as markers of iron storage, particularly in patients with infection and inflammation.